US & World

MRSA: The Drug-Resistant 'Superbug' That Won't Die

NPR|March 23, 2010

"Superbug," a new book by journalist Maryn McKenna, tracks the spread of MRSA, the drug-resistant staph infection that seems to outwit every antibiotic thrown at it. McKenna explains how the bacteria has changed over the past 30 years — and how a vaccine may be the only way to stop it.

For several decades, a highly-sophisticated bacteria called MRSA has spread rapidly through hospitals, communities and schools. MRSA, which stands for methicillin resistant Staphylococcus aureus, is a type of staph infection — the kind that can't be treated with first-line antibiotics.

Staph infections are the number one cause of both skin infections and infections in hospitals. Though most can be treated by antibiotics, the number of cases of MRSA is growing. By 1996, writes Maryn McKenna "almost every large hospital in the United States had detected at least one MRSA infection, and a third of all the staph infections that occurred during hospital stays were caused by MRSA instead of common drug-sensitive staph."

McKenna is the author of Superbug: The Fatal Menace of MRSA. In an interview with Fresh Air, she explains that from the 1960s, when doctors first started seeing patients with MRSA, until the 1990s, that "it was always thought that the only place where [MRSA] was successful in attacking people was in hospitals because [patients] are debilitated and ill."

But in the 1990s, doctors at the University of Chicago Medical Center began to notice young patients coming into the emergency room with MRSA. The young people had particularly severe cases — and unlike most patients diagnosed with drug-resistant staph infections, these patients had not contracted the pathogen inside a hospital setting.

"It turned out that there was a slightly different strain of staph that had adapted itself to live in the community and cause infections that are serious — and sometimes more serious — than the ones that were being caused in hospitals," says McKenna.

The second strain of MRSA was initially resistant to fewer drugs than the hospital strain — but acquired resistance to antibiotic treatment quickly. And now, the hospital MRSA strain and the community MRSA strain have merged to form a third kind of MRSA which, McKenna says, is even more dangerous.

"What [researchers] started to notice is that people were hospital patients and yet, were infected with the community strain — which meant that it behaved slightly differently, caused slightly different syndromes, and also was resistant to different drugs," says McKenna. "This makes it much harder to say when someone is infected with a MRSA infection, exactly which drugs are going to work. So you have to use the most intense drugs immediately until you can figure our which of the less-important drugs might work for the hospital or the community strain."

Because MRSA spreads through skin-to-skin contact, McKenna says that infections often spread in places where crowding and sanitation are concerns, like in prisons or army barracks.

"It [also] explains why [MRSA infections] tend to happen a lot in athletes and kids who play school sports. When a child crashes into another child in a football tackle — and one child has their on their skin, and the other child gets scraped — then the bacteria can enter their skin there," she says.

McKenna notes parents shouldn't worry about letting their kids play sports, but notes that it's important to make sure children are clean.

"There are things that kids do — such as not bringing their uniforms home to get washed very often or letting their shoulder pads get dirty — and then there are things that schools do as well," she says. "It was really astonishing to me to learn that kids no longer shower after gym class. ... They don't do that anymore. So if they've picked up a bacterium as they're out on the football field, it's going to be on their skin much longer."

Though MRSA is easily transmittable, McKenna says following simple hygienic steps can help prevent the pathogen from spreading.

"You can control washing your hands a lot," she says. "You can control if you live in a city with a subway — where lots of people are holding onto the subway rail — you can control having a bottle of something uncomplicated like Purell in your purse or in your pocket. You can control when you go to the doctor or take your kid to the doctor, when you're using drugs in an appropriate way. To go around in our lives feeling like there's this cloud or threat all the time puts us in the position where we tend to over-respond, and when we tend to over-respond, we use too many bacterial products. We use antibiotics inappropriately. And then without realizing it, we make worse the situation we've already gotten ourselves into with this epidemic of drug-resistant bacteria."

Interview Highlights

On how it's being spread beyond hospitals, into the community:

"MRSA lives not just in people who are debilitated and ill and who are in hospitals but in all of us walking around all the time. But it was always thought — from about the 1960s when it first sparked up to the 1990s — that the only place where it was successful in attacking people was in hospitals because [patients] are debilitated and ill. And then in the 1990s, a group of researchers at the University of Chicago noticed that they were seeing infections in children that looked very like those hospital infections and yet these kids had never been anywhere near a hospital. And it turned out that there was a slightly different strain of staph that had adapted itself to live in the community and cause infections that are serious — and sometimes more serious — than the ones that were being caused in hospitals."

On what MRSA can do the human body:

"The interesting thing about MRSA is that is does an extraordinary number of things that it's taken a number of years for people to figure out. So, MRSA is an acronym: M-R-S-A. And the S-A stands for Staphylococcus aureus, which is a very large grouping of bacteria which have been with mankind for probably as long as we've been human and you can tell that because there's a lot of tricks it has for getting around our immune system. It lives with us — on our skin, in our nostrils, often without causing very much difficulty until it can get inside our bodies through a scrape or a cut in the skin or an incision made for, say a catheter. Then, it can cause infestations of the valves of the heart. It can infect the inside of bones. It can cause very large abscesses — collections of pus inside muscles. More recently, it's been discovered that it doesn't actually need a cut or a break in the skin in order to cause disease. It can also start an infection on what looks like intact skin and cause what medicine calls 'a skin and soft tissue infection' which sounds like not a big deal but can turn into a very large infection that requires surgery to get better."

On why people in hospitals are more likely to be infected with the bacteria:

"People who are in hospitals are really good targets for infections. If you were a bacterium, you'd probably really like to live in [sick people] because their immune systems are damped down in a number of ways. They might be elderly. They might be taking chemotherapy — either for HIV or for cancer. They might have had a lot of other antibiotics already that damped down the immune system. They might have a lot of cuts on their skin because of lines and IVs going in and out. So they present both a lot of portals for which bacteria can enter and also reduced defenses in the body once the bacteria get in."

On why it's difficult to get rid of drug-resistant staph infections inside hospitals:

"There are lots of sick people and there are lots of really busy health care workers who, because medicine is so complicated, so technological, and ... so very, very busy, have a lot of things to do. So there are steps that they may miss. There are a lot of surveys now that say health care works often miss simple opportunities to wash their hands — as many as 50% of opportunities. Not because they're evil or because they intend to infect people, but because they're distracted and have very, very busy days. And there are bacteria — and staph is one of them — that can live on surfaces in hospitals. Unless things were absolutely sterile all the time, it is unlikely that we would be able to make hospitals completely resistant-bacteria free."

What makes MRSA the perfect pathogen:

"It's very difficult to act as thought it doesn't have a personality. It seems so smart. Not it's not in fact smart — it's in fact the blind persistence of natural selection. But natural selection seems to be working really well for staph. First, it has all this ability to live with us in a manner that is pretty much unchallengeable. We can't eradicate staph. It's part of our personal flora and part of our environment. Then, it has this really sophisticated system of defenses and work-arounds for our immune system. It's got abilities to turn on resistance factors. It's got a wide variety of genes that are specific to that. It also produces toxins that destroy muscle and burst cells. And in addition to all that virulence and all that ability to live on our body and in our environment, it's very smart in developing resistance as well."

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